When David Cameron last led a trade mission to India in July 2010, he had been Prime Minister for less than three months.

Amid the backslapping, games of cricket, garlands of marigolds and grand talk about a new special relationship, there were moments when the biggest British government delegation to visit India since the end of the Raj felt more like a Tory victory lap.

Nevertheless, looking red-faced and cheerful in the Delhi sunshine, Mr Cameron did seem earnest enough when he said that he had come to the emerging economic superpower in a “spirit of humility” in a push